21 years ago - Toni Moretti is born the daughter of a former US Senator (although truely the result of an alien breeding program).
7 years ago - 14-year-old Toni is teleported to her alien progenitors ship where her skin turns silver & she develops her plasma powers. she escapes back to earth with the help of Starfire & Nightwing.
6 years ago - 15-year-old Toni joins Flamebird's Titans as Argent. She is one of the only survivors of the Qurac bombing.
3 years ago - 18-year-old Toni is injured in battle that killed Donna Troy, and chooses to begin attending classes while she rehabilitates.
Argent was part of a Teen Titans membership composed entirely of new characters written just for that book, and a de-aged Atom. The new characters were all alien hybrids, all dealing with the discovery of their abilites. These new characters have all continued to participate in the Titans in one form or another, but only Argent continued to have a presence on the actual Titans, even being asked to serve as a member when the original character lineup got back together.
It's not hard to see why she was kept a part of the team: her ability to weild shapable plasma fields effectively made her a construct weilder like Green Lantern, one of the only classic characters to not have a counterpart in the Titans. She's just so incredibly useful, including her seems like a no-brainer.
So we've done exactly that. We included her in almost every Titans lineup after the downfall of the central team, and even tied her abduction by her alien progenitors to Starfire & Nightwing's time off-planet freeing Tamaran from the Citadel. She's now a veteran of the Titans, and when Wondergirl asks her to join the current line-up, it seems an obvious choice.